The present invention relates generally to a new engine for use in, for example, personal watercraft. In particular, the present invention relates to a new four-stroke in-line engine that was developed with a view to the future stricter environmental and emission regulations. The engine has an improved cooling system that combines both a closed loop cooling system with an open loop cooling system for enhanced cooling efficiency.
There is a very popular type of watercraft known as a xe2x80x9cpersonal watercraftxe2x80x9d which is designed to be operated primarily by a single rider. Although this type of watercraft is commonly employed for single riders, frequently provisions are made for accommodating additional passengers although the maximum number of passengers is more limited than conventional types of watercraft.
This type of watercraft is also generally quite sporting in nature and normally accommodates at least the rider on a type of seat in which the rider sits in a straddle fashion. The passenger""s area is frequently open through the rear of the watercraft so as to facilitate entry and exit of the rider and passengers to the body of water in which the watercraft is operating, as this type of watercraft is normally ridden with passengers that are wearing swimming suits.
These personal watercraft are generally quite small so that they can be conveniently transported from the owner""s home to a body of water for its use. Because of the small size, the layout of the components is extremely critical, and this gives rise to several design considerations that are peculiar to this type of watercraft. However, due to its sporting nature it is also desirable if the watercraft is powered by an engine and propulsion device that are not only efficient but also generate sufficient power.
Traditionally, two-cycle engines have been used to power watercraft, including personal watercraft. These engines have the advantage that they are fairly powerful, relatively lightweight, and compact.
One particular disadvantage to the two-cycle engine is its emission content. Two-cycle engines generally exhaust larger quantities of hydrocarbons and other pollutants than four-cycle engines due to cylinder charging inefficiencies and the combustion of lubricating oil among other things. When measures are taken to reduce emissions of the two-cycle engine, other generally undesirable consequences can result, such as an increase in the weight of the engine, a reduction of its power output or the like. With concern for the environment and increasingly strict emissions requirements being instituted by various governing bodies. There is motivation to provide a power plant that reduces exhaust emissions while retaining other advantageous characteristics such as compactness, low weight and high power output.
An engine cooling system for a two-cycle engine is disclosed in U.S. Pat. No. 5,820,426 to Hale, entitled xe2x80x9cExhaust System For Personal Watercraft.xe2x80x9d The cooling of the exhaust system is incorporated into open loop engine cooling water system in which water is drawn from outside the watercraft to cool the engine. In particular, pressurized cooling water is pumped through a cooling jacket in the exhaust manifold. The cooling jacket is linked to the water cooling system of the engine block. Since the cooling water is drawn from outside the watercraft, it may contain dirt and other debris, which may clog the cooling system and damage the engine.
Four-cycle engines are commonly used as power plants in other applications, such as automobiles. These engines have the advantage that their emissions output are generally desirably lower as compared to a two-cycle engine for a given power output.
It is an object of the present invention to provide a four stroke, in-line engine having a compact construction.
It is another object of the present invention to provide a four stroke, in-line engine having a modular construction to permit the interchange of parts between various engine models.
It is another object of the present invention to provide a four stroke, in-line engine having improved exhaust emission characteristics.
It is another object of the present invention to provide a four stroke engine having a narrow and low profile.
It is another object of the present invention to provide a four stroke engine having a low profile valve actuation assembly for controlling the operation of the intake and exhaust valves.
It is another object of the present invention to provide a cylinder head having a low profile to reduce engine height.
It is another object of the present invention to offset the placement of the intake valves and exhaust valves with respect to a vertical axis within the cylinder head to reduce engine height.
It is another object of the present invention to provide an improved spark plug mounting assembly for easy access within the cylinder head.
It is another object of the present invention to provide a Y-shaped intake rocker arm assembly providing a compact construction.
It is yet another object of the present invention to provide a four stroke engine having an improved oil collection system and oil holding tank.
It is another object to provide a four stroke engine which combines a closed loop cooling system and an open loop cooling system for enhanced cooling of the engine in accordance with the present invention.
It is another object to provide an open loop cooling system for cooling an exhaust manifold in accordance with the present invention, wherein the open loop cooling system enhances cooling of the crankcase and cylinder head.
It is another object to provide an open loop cooling system for cooling an exhaust manifold in accordance with the present invention, wherein the open cooling system lowers the temperature of the exhaust manifold such that the exhaust manifold functions as a heat sink for the crankcase and cylinder head.
It is another object of the present invention to provide a closed loop cooling system for selectively cooling the crankcase and cylinder head of the four stroke engine.
It is another object of the present invention to provide a closed loop cooling system having a selectively operable heat exchanger.
In accordance with the present invention, a four stroke internal combustion engine is disclosed. In a preferred form, the engine has an in-line configuration with at least one cylinder. The engine includes a crankcase, and a cylinder head connected to the crankcase. The cylinder head and the crankcase together form at least one cylinder. Each cylinder includes at least one intake valve and at least one exhaust valve. The engine in accordance with the present invention further includes a valve actuation assembly for operating the intake valves and the exhaust valves. The engine also includes a cooling system for cooling the engine and an engine control system.
In accordance with the present invention, the cooling system includes a closed loop cooling system for cooling at least a portion of the engine. The cooling system also includes an open loop cooling system for cooling at least a portion of the engine. The open loop cooling system uses coolant from an external source (e.g., a body of water) to cool the exhaust manifold and the exhaust gases.
In accordance with the present invention, the closed loop cooling system includes at least one coolant passageway extending around a portion of the cylinders. The coolant passageway is adapted to contain coolant to remove heat generated by the cylinder during engine operation. The coolant passageway is located within the crankcase and also extends through at least a portion of the cylinder head.
The closed loop cooling system further includes at least one coolant pump for pumping the coolant through the at least one coolant passageway. A heat exchanger is provided for selectively removing heat from the coolant at predetermined engine operating conditions. The heat exchanger is inactive during an engine start-up operation.
The engine further includes a lubrication system for providing lubricant to the engine having at least one lubricant pump for pumping lubricant through the engine. It is contemplated that the lubricant pump may be operatively connected to the coolant pump. The closed loop cooling system also includes a lubricant cooler for cooling the lubricant in the lubrication system at predetermined engine operating conditions.
In accordance with the present invention, the open loop cooling system cools the exhaust gas and the exhaust manifold. An exhaust manifold is connected to the cylinder head and operatively connected to an exhaust passageway in the cylinder head.
The open loop cooling system includes a first exhaust coolant passageway extending around at least a portion of the exhaust manifold. The exhaust manifold includes an inner manifold, and an outer manifold surrounding the inner manifold. The inner manifold and the outer manifold are connected to one another to define the exhaust coolant passageway. The open loop cooling system further includes at least one inlet port to permit coolant to enter the coolant passageway from an external source and at least one exhaust port, permitting egress of coolant from the coolant passageway.
A second exhaust manifold is connected to the exhaust manifold. The open loop cooling system includes a second exhaust coolant passageway extending around at least a portion of the second exhaust manifold. The second exhaust manifold includes an inner manifold, and an outer manifold surrounding the inner manifold. The inner manifold and the outer manifold are connected to one another to define the exhaust coolant passageway. The open loop cooling system further includes at least one inlet port to permit coolant to enter the coolant passageway from an external source and at least one exhaust port, permitting egress of coolant from the coolant passageway.
The present invention is also directed to a personal watercraft. The personal watercraft includes a hull, a seat assembly located on the hull and adapted to accommodate at least one passenger, and a four stroke internal combustion engine located within the hull. The internal combustion engine includes a crankcase secured to the hull, and a cylinder head connected to the crankcase. The cylinder head and the crankcase together form at least one cylinder. Each cylinder has at least one intake valve and at least one exhaust valve associated therewith. A valve actuation assembly operates the intake and exhaust valves. The engine further includes a cooling system for cooling the engine. The cooling system includes a closed loop cooling system for cooling at least a portion of the engine having at least one coolant passageway extending around a portion of the at least one cylinder, and an open loop cooling system for cooling at least a portion of the engine.
The present invention is also directed to a cooling system for an internal combustion engine. The cooling system includes a closed loop cooling system for cooling at least a portion of the engine. The closed loop cooling system includes at least one coolant passageway extending around a portion of the at least one cylinder. The coolant passageway is adapted to contain coolant to remove heat generated within the cylinder during engine operation. The cooling system further includes an open loop cooling system for cooling at least a portion of the engine. The closed loop cooling system cools at least a portion of one of the crankcase and the cylinder head. The open loop cooling system cools the exhaust gas in the exhaust manifold and at least a portion of one of the crankcase and the cylinder head.